There is provided an electric circuit such as an inverter circuit in air conditioners which provide a vapor compression refrigeration cycle with refrigerant circulating therein. Such an inverter circuit controls a motor of a compressor. In the inverter circuit, a power element which generates high heat is commonly employed. Conventional air conditioners include a cooling means configured to cool the power element, to prevent the temperature of the power element from exceeding the operable temperature range thereof. Examples of the cooling means include a cooling means configured to cool the power element by the refrigerant used in refrigeration cycle (for example, see Patent Document 1). As described in Patent Document 1, in an air conditioner, a refrigerant jacket has a refrigerant passageway (heatsink in Patent Document 1) through which the refrigerant used in refrigeration cycle flows. A power element (giant transistor in Patent Document 1) is fixed to the refrigerant jacket, and the refrigerant jacket is included in a switch box (electric component box).